After about 10-12 hours of playback, sound abruptly cuts out. When it does so, the playback software on the VM roughly doubles the rate at which it is "outputting" sound. I imagine this is because some component downstream is emptying the soundcard buffer faster than it would ordinarily, perhaps because it has experienced some failure and is emptying the buffer fast to keep the guest from freezing?

To get sound working properly again I only need to restart the playback application, not the VM or host OS.

The backend device is ALSA, sent through dmix. The VBox log file contains nothing particularly interesting except for a pair of PIT reconfigure messages when I stop and restart the playback app. ALSA sound capture is intentionally redirected to null.

I haven't tried Pulse output as Pulse isn't installed on the box in question. OSS output selects the wrong sample rate (plays 44.1khz guest output at 48khz, leading to a slight chipmunk effect) so I haven't used it for any significant amount of time.

So obviously this isn't a very useful bug report yet. How do I get more detailed information about what's going on in the audio backend?